| 主权项 |
1. An exhaust purification system of internal combustion engine in which an exhaust purification catalyst is arranged in an engine exhaust passage, a hydrocarbon feed valve is arranged in the engine exhaust passage upstream of the exhaust purification catalyst, precious metal catalysts are carried on exhaust gas flow surfaces of the exhaust purification catalyst, basic exhaust gas flow surface parts are formed around the precious metal catalysts, the exhaust purification catalyst has a property of reducing NOX which is contained in an exhaust gas if a concentration of hydrocarbons which flow into the exhaust purification catalyst is made to vibrate by within a predetermined range of amplitude and within a predetermined range of period and has a property of being increased in storage amount of NOX which is contained in the exhaust gas if the vibration period of the hydrocarbon concentration is made longer than the predetermined range, and, at the time of engine operation, hydrocarbons are injected from the hydrocarbon feed valve by the predetermined period to thereby remove the NOX which is contained in the exhaust gas, wherein hydrocarbons are injected from the hydrocarbon feed valve toward an upstream side of the engine exhaust passage and, when hydrocarbons are injected from the hydrocarbon feed valve by the predetermined period, an injection pressure of hydrocarbons is gradually reduced from a start of injection toward an end of injection in an injection period of each injection, the injection pressure of hydrocarbons at the time of said start of injection and the injection pressure of hydrocarbons at the time of said end of injection being set to injection pressures whereby hydrocarbons which are injected later are superposed with previously injected group of hydrocarbons. |
